Looks like you are doing the right things.
Cats will come to you when they are ready. The worst thing you can do is force yourself on them. They need to trust you and you cultivate this trust by leaving them alone so they know you are not a danger.
Eventually they will come out of their shell when they know they are safe. A new house is a scary place for a cat as they can smell and hear far more than you can perceive, so it is not just the visible physical environment they need to come to terms with, it is everything else too.
When we rescued ours, we just let them out of the pet carrier and left them to it. We made sure they had food, water, a bed and a litter tray and we let them have the run of the house. They were both very nervous but being brothers they took comfort in each other and were soon exploring and playing. We kept them in for 4 weeks before allowing them to venture out, and up until that point they had never been outside before. So it was a scary time for them and us!
They soon got comfortable with the house and us, it just takes a little time. Try and learn their personalities and insecurities. Our one cat refused to use a catflap for 2 years. Tried every which way to train him but he was having none of it. Then he went missing for a week or so. We were fearing the worst until one day he just came through the catflap like he had done it all his life. Now he uses it with no problems. Weird!
The other one is scared stiff of bin lorries. As soon as he hears one coming he will bolt for his spot under our bed and stay there for at least an hour.
If you try and handle him and show him there is nothing to be afraid of he gets very distressed. So we leave him to hide and he comes out when he is ready.
Just take it slow and let your cat learn to trust you
He will soon be using you as a radiator
